The invention relates to belt drive systems and more particularly to engine belt drive systems having automatic belt tension control.
Most engines used for automobiles and the like include a number of belt driven accessory systems that are necessary for the proper operation of the vehicle. The accessory systems may include an alternator, air conditioner compressor and power steering pump.
The accessory systems are generally mounted on a front surface of the engine. Each accessory having a pulley mounted on a shaft for receiving power from some form of belt drive. In early systems, each accessory was driven by a separate belt that ran between the accessory and the crankshaft. With improvements in belt technology, single serpentine belts were developed and are now used in most applications. Accessories are driven by a single serpentine belt routed among the various accessory components. The serpentine belt is driven by the engine crankshaft.
Since the serpentine belt must be routed to all accessories, it has generally become longer than its predecessors. To operate properly, the belt is installed with a pre-determined tension. As it operates, it may stretch slightly. This results in a decrease in belt tension, which may cause the belt to slip. Consequently, a belt tensioner is used to maintain the proper belt tension as the belt stretches during use. A belt tension may be controlled by movement of pulleys as well as through the use of tensioners.
Control systems are known which allow a user to adjust a belt tension during operation of the system. These systems generally use a cylinder or other mechanical device to adjust a drive wheel position. The control system may also adjust a belt tension in response to belt speed.
Representative of the art is Japanese Publication No. 2001-059555 to Denso which discloses a belt transmission system to control slipping of a belt by computing a slip factor from a detection value from a first and second tachometer, the first tachometer detecting an engine speed and the second tachometer detecting an auxiliary module speed.
Also representative of the art is U.S. Pat. No. 5,641,058 (1997) to Merten er al. which discloses a invention which employs pressure and displacement sensors for the automatic monitoring and adjustment of endless belts by movement of drive and return wheels.
The prior art does not allow active control of belt tension to reduce belt slip while increasing belt life by setting a low belt tension when low tension is all that is required, but increasing tension momentarily and temporarily when such is necessary during transient conditions to prevent belt slip and associated noise.
What is needed is a belt tension control system having sensors for detecting a. belt operating condition. What is needed is a belt tension control system having a control module for using belt operating condition signals to actively control an actuator. What is needed is a belt tension control system for increasing a belt life by actively controlling a belt tension. What is needed is a belt tension control system capable of anticipating and preventing a belt slip noise event. The present invention meets these needs.
The primary aspect of the invention is to provide a belt tension control system having an actuator controlled by a control module for moving a pivoted pulley to adjust a belt tension.
Another aspect of the invention is to provide a belt tension control system having sensors for detecting a belt operating condition.
Another aspect of the invention is to provide a belt tension control system having a control module for using belt operating condition signals to actively control an actuator.
Another aspect of the invention is to provide a belt tension control system for increasing a belt life by actively controlling a belt tension.
Another aspect of the invention is to provide a belt tension control system capable of anticipating and preventing a belt slip noise event.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a belt drive system for automatically controlling a belt tension. The system comprises an actuator controlled by a control module. The actuator operates on a pivoted pulley. A belt is trained about the pivoted pulley as well as other pulleys driving various accessories. A series of sensors in the system detect a belt condition including a belt tension. Sensor signals are transmitted to the control module. The control module processes the signals and instructs the actuator to move the pivoted pulley, thereby increasing or decreasing a belt tension. A feedback loop from the sensors to the control module allows the belt tension to be continuously monitored and adjusted many times per second. The system may actively control a belt tension by anticipating a system condition to prevent a belt noise by comparing sensor signals to a system model stored in a control module memory.